In recent years, reflecting diversification of consumers' tastes and increasing health consciousness, a wide variety of health foods have been put on the market and are finding a broadening demand. For example, polyphenols are known to have antioxidant activities, and owing to their expected effects such as anti-arteriosclerosis, antiallergy and blood stream enhancement, they are recognized as an important ingredient for health foods.
These polyphenols can be obtained, for example, as a polyphenol fraction by bringing an aqueous extract solution of oolong tea into contact with activated carbon or an adsorbent resin to eliminate the non-polymer catechins (Patent Document 1).